Mammography is the current cost-effective gold standard for breast cancer screening. However, its usefulness has recently become a subject of considerable debate. The limitations of mammography are most evident in the population of women who have dense breast tissue where up to half the cancers can be missed. Furthermore, mammography generates radiation and can be quite uncomfortable. While magnetic resonance imaging (MRI) can be more accurate than mammography, it is not practical because it is too expensive for routine use. Currently, there is a trade-off between the cost effectiveness of mammography on the one hand and the imaging accuracy of MRI on the other. This trade-off represents a barrier to increasing survival rates for women who develop breast cancer. Our long-term goal is to eliminate this trade-off and thereby improve breast cancer survival rates through the introduction of safe, cost-effective, operator-independent sonography based on the principles of ultrasound tomography (UST). The objective of this study, and the next step in pursuit of that goal, is to demonstrate that our new UST scanner is ready to become a clinical and commercial product. The study is justified by the fact that our prior work has already demonstrated the feasibility of breast imaging with UST while the new design promises to greatly increase the performance of the scatter. By demonstrating the improved performance we will be able to introduce a practical, low-cost product for breast cancer screening and diagnosis with potential for significant societal impact. We propose to test the SoftVue system in the lab (Phase I) and then in the clinic (Phase II) to determine its performance and readiness for the marketplace. This study is expected to generate supportive evidence for regulatory clearance and important input for planning large scale screening trials so that the company can undertake its Phase III activities of (i) selling SoftVue scanners for the diagnostic marketplace and (ii) undertaking screening trials to support future regulatory approval for screening. PUBLIC HEALTH RELEVANCE: The lack of an alternative breast imaging method that obviates the constraints of current standard imaging modalities is a barrier to dramatically impacting mortality (about 45,000 women in the US per year) and morbidity from breast cancer. Currently, there is a trade-off between the cost effectiveness of mammography and sonography on the one hand and the imaging accuracy of dynamic contrast enhanced magnetic resonance (DCE-MR) on the other. The work described in this proposal will potentially eliminate this trade-off by combining the low- cost advantage of mammography with the superior imaging performance of DCE-MR through the development of an ultrasound tomography scanner (UST). Furthermore, UST offers comfort, operator independence and low-installation and maintenance costs. These advantages will be very beneficial to the society as they will support early breast cancer detection, decrease in the number of unnecessary biopsies, improved participation in breast cancer screening programs, and ultimately improved breast cancer survival rates.